1. Field of the Invention
The present invention relates to an endoscopic instrument which continuously ligates living tissues in a medical treatment for a gastric or esophageal varix or excision for a polyp or mucosa.
2. Description of the Related Art
Generally, as an apparatus enabling continuous ligation of living tissues, for example, a ligator a having a structure shown in FIG. 17 (Saeed Multi-Band Ligators Sixshooter Wilson-Cook Medical Inc.) is commercially available.
A tubular member b which can be attached to an end of an insertion portion of an endoscope h is provided to this ligator a, as shown in FIGS. 18A and 18B. A plurality of, which is six in this example, ring elastic ligation bands c1 to c6 are sequentially expanded and wound around the outer peripheral surface of the tubular member b.
Further, two operation cords f and g which can be inserted into a channel h1 in the endoscope h are provided to the ligator a. Six operation beads d1 to d6 whose number is equal to that of the elastic ligation bands c1 to c6 are fixed at an end portion of one operation cord f. Similarly, six operation beads e1 to e6 are fixed at an end portion of the other operation cord g. Furthermore, the respective operation beads d1 to d6 and e1 to e6 are engaged with the respective ligation bands c1 to c6. As a result, the respective operation beads d1 to d6 and e1 to e6 are set on the outer peripheral surface of the tubular member b together with the ligation bands c1 to c6. Moreover, the operation cords f and g are inserted into the channel h1 of the endoscope h and extended to the operation portion of the endoscope h.
In addition, when using the ligator a, an operator causes living tissues to be sucked into the tubular member b through the channel h1 of the endoscope h. Thereafter, the ring elastic ligation bands c1 to c6 are sequentially drawn from the end portion side of the tubular member b toward the end portion by pulling the operation cords f and g toward the front side. As a result, the ligation bands c1 to c6 can be removed from the tubular member b in order. At this moment, with the respective ligation bands c1 to c6 being wound around the living tissues sucked to the tubular member b, the living tissues at a plurality of positions can be ligated.
Additionally, for example, U.S. Pat. No. 5,735,861 discloses an operation instrument i which facilitates the operation for pulling the two operation cords f and g of the ligator a toward the front side (see FIGS. 19A to 19C). To the operation instrument i illustrated in this example is provided a substantially U-shaped bearing holder j as shown in FIG. 19A. A take-up shaft m which takes up the operation cords f and g is rotatably supported by the holder j. A handle n is connected to one end portion of the take-up shaft m. Further, a base end portion of a tubular insertion shaft t is connected to the holder j through a tapered shaft portion t1.
Furthermore, when using the operation instrument i, as shown in FIG. 19B, the two operation cords f and g are drawn to the take-up shaft m side of the holder j through the channel h1 of the endoscope h and the lumen of the insertion shaft t of the operation instrument i and fixed to the take-up shaft m. In this state, the insertion shaft t is inserted into a mouth ring portion h3 of the channel h1 opened to the operation portion h2 of the endoscope h as shown in FIG. 19C. Moreover, the operation cords f and g are wound around the take-up shaft m by rotating the handle n of the operation instrument i. As a result, the ligation bands c1 to c6 are removed from the tubular member b in order, thereby ligating the living tissues.
In addition, an airtight valve s such as a forceps tap is attached to the mouth ring portion h3 of the channel h1 of the endoscope h as shown in FIG. 19B. Additionally, as shown in FIG. 19C, when the insertion shaft t of the operation instrument i is inserted into the mouth ring portion h3 of the channel h1 of the endoscope h through the airtight valve s, the operation instrument i can be detachably engaged with the mouth ring portion h3 of the channel h1 in the endoscope h.
Meanwhile, the airtight valve s such as a forceps tap attached to the mouth ring portion h3 of the channel h1 in the endoscope h is generally constituted by an elastic member such as rubber. Therefore, when the insertion shaft t of the operation instrument i disclosed in U.S. Pat. No. 5,735,861 is inserted into and fixed to the mouth ring portion h3 of the channel h1 in the endoscope h through the airtight valve s, a problem such as unstableness occurs even after the operation instrument i is attached to the mouth ring portion h3 of the channel h1 in the endoscope h, and the operation instrument i can not be stabilized.
Further, the tapered shaft t1 of the insertion shaft t and a tapered hole u on the inner surface of the channel h1 on the opening end portion side are fixed to each other by frictional engagement as shown in FIG. 19C. Therefore, fixation of the operation instrument i becomes loose when the strong force is applied to the insertion shaft t of the operation instrument i in order to ligate the living tissues, and the operational feeling when rotating the handle n of the operation instrument i may be possibly deteriorated.
On the other hand, when applying the tension to the operation cord f in order to remove the ligation bands c1 to c5, the handle n must be always held in order to prevent the handle n from rotating in the reverse direction due to reaction force, which degrades the operational feeling. As a method for solving this problem, there is an operation instrument (Speedband Multiple Band Ligator Boston Scientific Corp.) shown in FIGS. 20 to 23 as a commercially available prior art product.
This is a product obtained by providing a one-way clutch which prevents the take-up shaft m from rotating in the reverse direction to the main body of the operation instrument as shown in FIG. 21. The one-way clutch prevents the take-up shaft m from rotating in the reverse direction when an engagement claw p of a spring o fixed to the main body of the operation instrument is engaged with recess portions q1 and q2 provided on the outer periphery of the take-up shaft m at a fixed interval r. Here, the recess portions q1 and q2 have a length corresponding to an interval r′ required for each of the elastic ligation rings c1 to c5 to be removed from the tubular member. Therefore, the ligation bands c1 to c5 are removed from the end every time the claw p engages with the recess portions q1 and q2. That is, one of the ligation bands c1 to c5 is removed per click caused due to engagement of the claw p with the recess portion q.
The operation instrument having the structure shown in FIGS. 20 to 23 has the following problem.
The ligation bands are removed one by one every time one click occurs which is generated due to engagement of the claw p with the recess portions q1 and q2 at fixed intervals r. On the other hand, since the entire length of the channel of the non-illustrated endoscope differs depending on models, the phase between the interval r on the front side and interval r′ at which the ligation bands are removed varies in accordance with each model of the endoscope. When the phase difference becomes maximum, there occurs a problem that the ligation bands c1 to c6 stop during movement on the tubular member b.
Thus, in the operation instrument having the structure shown in FIGS. 20 to 23, the operation portion i is attached to the endoscope, the recess portions q1 and q2 are then set to initial positions, and the operation cord f is thereafter fixed to a slit w of the take-up shaft m without slacks. As a result, the phase of the interval r on the front side and the interval r′ on the end side can be uniquely determined irrespective of the entire length of the channel of the endoscope.
However, engagement of the operation cord f with the slit w must withstand the capacity for operating the ligation bands c1 to c5. Therefore, in the structure shown in FIGS. 20 to 23, the operation cord f is led out from a lead-out hole x (shown in FIG. 20) of the take-up shaft m through a side hole y (shown in FIG. 23) of the take-up shaft m and fixed to the slit w provided to the side surface y, which complicates the structure and the operation.